It really depends on your lights and how well you can cool your setup. With a MH you'll have to stay about 12" away due to the amount of heat it puts out, but my 400W HPS in air-cooled tube can get much closer than that. CFLs should never be more than a few inches a way.
Always try to keep your plants as close to your lights as possible. Just be sure they don't burn! Something you should check about every day.
I keep my veg light 6 in or less from the tops is t5 with 4 bulbs and flower is 15 in from tops air cooled 1000 watt You loose less light the closer they are to the plants which means more plant and that's a good thing lol Sent from iPhone 5
Ya. I got a 600 hps/mh but its sitting at the bottom. I can adjust my temp fine. Ill fix tonight. What's the purpose?
I understand you lose light the farther they are but my plants about 2-3 weeks behind. Wondering if this could be the cause.
You should be able to get a six hundred like 12 inches away if its air cooled then 15 to 20 if not If you put your hand above the top and its not bad then your plants will be ok Sent from iPhone 5